The prevention of accidents is one of the most important goals of ad hoc networks in smart cities. When an accident happens, dynamic sensors (e.g., citizens with smart phones or tablets, smart vehicles and buses, etc.) could shoot a video clip of the accident and send it through the ad hoc network. With a video message, the level of seriousness of the accident could be much better evaluated by the authorities (e.g., health care units, police and ambulance drivers) rather than with just a simple text message. Besides, other citizens would be rapidly aware of the incident. In this way, smart dynamic sensors could participate in reporting a situation in the city using the ad hoc network so it would be possible to have a quick reaction warning citizens and emergency units. The deployment of an efficient routing protocol to manage video-warning messages in mobile Ad hoc Networks (MANETs) has important benefits by allowing a fast warning of the incident, which potentially can save lives. To contribute with this goal, we propose a multipath routing protocol to provide video-warning messages in MANETs using a novel game-theoretical approach. As a base for our work, we start from our previous work, where a 2-players game-theoretical routing protocol was proposed to provide video-streaming services over MANETs. In this article, we further generalize the analysis made for a general number of N players in the MANET. Simulations have been carried out to show the benefits of our proposal, taking into account the mobility of the nodes and the presence of interfering traffic.Finally, we also have tested our approach in a vehicular ad hoc network as an incipient start point to develop a novel proposal specifically designed for VANETs.

Nowadays, people expectations for ubiquitous connectivity is continuously growing. Cities are now moving towards the smart city paradigm. Electricity companies aims to become part of smart grids. Internet is no longer exclusive for humans, we now assume the Internet of everything. We consider that Wireless Mesh Networks (WMNs) have a set of valuable features that will make it an important part of such environments. WMNs can also be use in less favored areas thanks to their low-cost deployment. This is socially relevant since it facilitates the digital divide reduction and could help to improve the population quality of life. Research and industry have been working these years in open or proprietary mesh solutions. Standardization efforts and real deployments establish a solid starting point.We expect that WMNs will be a supporting part for an unlimited number of new applications from a variety of fields: community networking, intelligent transportation systems, health systems, public safety, disaster management, advanced metering, etc. For all these cases, the growing needs of users for real-time and multimedia information is currently evident. On this basis, this thesis proposes a set of contributions to improve the performance of an application service of such type and to promote the better use of two critical resources (memory and energy) of WMNs.For the offered service, this work focuses on a Video on Demand (VoD) system. One of the requirements of this system is the high capacity support. This is mainly achieved by distributing the video contents among various distribution points which in turn consist of several video servers. Each client request that arrives to such video server cluster must be handled by a specific server in a way that the load is balanced. For such task, this thesis proposes a mechanism to appropriately select a specific video server such that the transfer time at the cluster could be minimized.On the other hand, mesh routers that creates the mesh backbone are equipped with multiple interfaces from different technologies and channel types. An important resource is the amount of memory intended for buffers. The quality of service perceived by the users are largely affected by the size of such buffers. This is because important network performance parameters such as packet loss probability, delay, and channel utilization are highly affected by the buffer sizes. An efficient use of memory for buffering, in addition to facilitate the mesh devices scalability, also prevents the problems associated with excessively large buffers. Most of the current works associate the buffer sizing problem with the dynamics of TCP congestion control mechanism. Since this work focuses on real time services, in which the use of TCP is unfeasible, this thesis proposes a dynamic buffer sizing mechanism mainly dedicated for such real time flows. The approach is based on the maximum entropy principle and allows that each device be able to dynamically self-configure its buffers to achieve more efficient memory utilization. The proper performance of the proposal has been extensively evaluated in wired and wireless interfaces. Classical infrastructure-based wireless and multi-hop mesh interfaces have been considered. Finally, when the WMN is built by the interconnection of user hand-helds, energy is a limited and scarce resource, and therefore any approach to optimize its use is valuable. For this case, this thesis proposes a topology control mechanism based on centrality metrics. The main idea is that, instead of having all the devices executing routing functionalities, just a subset of nodes are selected for this task. We evaluate different centralities, form both centralized and distributed perspectives. In addition to the common random mobility models we include the analysis of the proposal with a socially-aware mobility model that generates networks with a community structure.

Nodes in wireless multi-hop networks establish links with their neighbors, which are used for data transmission. In general, in this kind of networks every node has the possibility of acting as a router, forwarding the received packets when they are not the final destination of the carried data. Due to the routing protocol procedures, when the network is quite dense the overload added by the routing management messages can be very high. To reduce the effects of this overload a topology control mechanism can be used, which can be implemented using different techniques. One of these techniques consists of enabling or disabling the routing functionality in every node. Many advantages result from selecting just a subset of nodes for routing tasks: reduction of collisions, protocol overhead, interference and energy consumption, better network organization and scalability. In this paper, a new protocol for topology control in wireless mesh networks is proposed. The protocol is based on the centrality metrics developed by social network analysts. Our target network is a wireless mesh network created by user hand-held devices. For this kind of networks, we aim to construct a connected dominating set that includes the most central nodes. The resulting performance using the three most common centrality measures (degree, closeness and betweenness) is evaluated. As we are working with dynamic and decentralized networks, a distributed implementation is also proposed and evaluated. Some simulations have been carried out to analyze the benefits of the proposed mechanism when reactive or proactive routing protocols are used. The results confirm that the use of the topology control contributes to a better network performance. (C) 2014 Elsevier B.V. All rights reserved.

Nodes in wireless multi-hop networks establish links with their neighbors, which are used for data transmission. In general, in this kind of networks every node has the possibility of acting as a router, forwarding the received packets when they are not the final destination of the carried data. Due to the routing protocol procedures, when the network is quite dense the overload added by the routing management messages can be very high. To reduce the effects of this overload a topology control mechanism can be used, which can be implemented using different techniques. One of these techniques consists of enabling or disabling the routing functionality in every node. Many advantages result from selecting just a subset of nodes for routing tasks: reduction of collisions, protocol overhead, interference and energy consumption, better network organization and scalability. In this paper, a new protocol for topology control in wireless mesh networks is proposed. The protocol is based on the centrality metrics developed by social network analysts. Our target network is a wireless mesh network created by user hand-held devices. For this kind of networks, we aim to construct a connected dominating set that includes the most central nodes. The resulting performance using the three most common centrality measures (degree, closeness and betweenness) is evaluated. As we are working with dynamic and decentralized networks, a distributed implementation is also proposed and evaluated. Some simulations have been carried out to analyze the benefits of the proposed mechanism when reactive or proactive routing protocols are used. The results confirm that the use of the topology control contributes to a better network performance.

Many proposals have studied the optimization of
the EDCA mechanism used by the IEEE 802.11p MAC layer to
provide QoS. In this work, we focus on the queuing process done
by the different Access Categories (ACs). We propose the use
of a single common buffer with a prioritized buffer allocation
algorithm inspired on the MAX-MIN principle for a fair sharing
of a common resource. We test the proposed algorithm with a
fixed and a dynamic guaranteed queue size for each AC. Results
obtained from simulations in a multihop VANET scenario show
that our approach outperforms traditional queuing used in MAC
802.11p.

This paper proposes a mixed linear and integer optimization model for multi-hop ad-hoc networks to select the positions of the gateways over a certain area. This model mimics the routing behavior of such network and takes into account the maximum bandwidth capacity of the network gateways. We also include a suboptimal solution for the cases in which the complexity or the amount of the data make the optimal solution infeasible. Results in a pedestrian mesh network and in a VANET scenarios show that the model locates gateways in an efficient way and that the suboptimal solution is close to the optimal one in terms of the number of required gateways or the common selected gateways.

Buffer overflow is an important phenomenon in data networks that has much bearing on the overall network performance. Such overflow critically depends on the amount of storage space allotted to the transmission channels. To properly dimension this buffering capacity a detailed knowledge of some set of probabilities is needed. In real practice, however, that information is seldom available, and only a few average values are at the analyst disposal. In this paper, the use of a solution to this quandary based on maximum entropy is proposed. On the other hand, when wireless devices are taken into account, the transmission over a shared medium imposes additional restrictions. This paper also presents an extension of the maximum entropy approach for this kind of devices. The main purpose is that wireless nodes become able to dynamically self-configure their buffer sizes to achieve more efficient memory utilization while keeping bounded the packet loss probability. Simulation results using different network settings and traffic load conditions demonstrate meaningful improvement in memory utilization efficiency. This could potentially benefit devices of different wireless network technologies like mesh routers with multiple interfaces, or memory constraint sensor nodes. Additionally, when the available memory resources are not a problem, the buffer memory reduction also contributes to prevent the high latency and network performance degradation due to overbuffering. And it also facilitates the design and manufacturing of devices with faster memory technologies and future all-optical routers.

In recent years, the general interest in routing for vehicular ad hoc networks (VANETs) has increased notably. Many proposals have been presented to improve the behavior of the routing decisions in these very changeable networks. In this paper, we propose a new routing protocol for VANETs that uses four different metrics. which are the distance to destination, the vehicles' density, the vehicles' trajectory and the available bandwidth, making use of the information retrieved by the sensors of the vehicle, in order to make forwarding decisions, minimizing packet losses and packet delay. Through simulation, we compare our proposal to other protocols, such as AODV (Ad hoc On-Demand Distance Vector), GPSR (Greedy Perimeter Stateless Routing), I-GPSR (Improvement GPSR) and to our previous proposal, GBSR-B (Greedy Buffer Stateless Routing Building-aware). Besides, we present a performance evaluation of the individual importance of each metric to make forwarding decisions. Experimental results show that our proposed forwarding decision outperforms existing solutions in terms of packet delivery.

In recent years, the general interest in routing for vehicular ad hoc networks (VANETs) has increased notably. Many proposals have been presented to improve the behavior of the routing decisions in these very changeable networks. In this paper, we propose a new routing protocol for VANETs that uses four different metrics. which are the distance to destination, the vehicles’ density, the vehicles’ trajectory and the available bandwidth, making use of the information retrieved by the sensors of the vehicle, in order to make forwarding decisions, minimizing packet losses and packet delay. Through simulation, we compare our proposal to other protocols, such as AODV (Ad hoc On-Demand Distance Vector), GPSR (Greedy Perimeter Stateless Routing), I-GPSR (Improvement GPSR) and to our previous proposal, GBSR-B (Greedy Buffer Stateless Routing Building-aware). Besides, we present a performance evaluation of the individual importance of each metric to make forwarding decisions. Experimental results show that our proposed forwarding decision outperforms existing solutions in terms of packet delivery.

In this paper, a new mechanism for topology control in wireless
mesh networks is proposed. We evaluate the application to this
problem of the centrality metrics developed by social network
analysts. Our target network is a wireless mesh network created
by user hand-held devices. For this kind of networks, we aim to
construct a connected dominating set that includes the most
central nodes. Many advantages result from selecting just a subset
of stations for routing tasks: reduction of collisions, protocol
overhead, interference and energy consumption, better network
organization and scalability. The resulting performance using the
three most common centrality measures (degree, closeness and
betweenness) is evaluated. As we are working with dynamic and
decentralized networks, a distributed implementation is also
proposed and evaluated.

In this paper, a new mechanism for topology control in wireless
mesh networks is proposed. We evaluate the application to this
problem of the centrality metrics developed by social network
analysts. Our target network is a wireless mesh network created
by user hand-held devices. For this kind of networks, we aim to
construct a connected dominating set that includes the most
central nodes. Many advantages result from selecting just a subset
of stations for routing tasks: reduction of collisions, protocol
overhead, interference and energy consumption, better network
organization and scalability. The resulting performance using the
three most common centrality measures (degree, closeness and
betweenness) is evaluated. As we are working with dynamic and
decentralized networks,

Mobile ad hoc networks (MANETs) are infrastructureless
networks formed by wireless mobile devices. Recently,
the demand over multimedia services such as video streaming
has increased specially since the number of mobile end users is
growing as well. MPEG-2 VBR is one of the most fitting video
coding techniques for MANETs which improves the distribution
of video streams specially when it is used with a proper multipath
routing scheme. In this article, we aimed to design a routing
scheme to dynamically select the forwarding paths using a
game-theoretic approach over a multipath routing protocol. Our
proposal seeks to describe an equation of the probability p of
sending video frames through the best available path. p depends
on network parameters that vary throughout time. The aim is
that the most important video frames (I+P) will be sent through
the best path with a certain probability p and will be sent through
the second best path with a probability 1-p. To achieve that, we
carried out simulations done with fixed values of p and after that
we applied a lineal regression method to obtain the coefficients
of the equation for p. Simulations have been done to show the
benefits of our proposal where interfering traffic and mobility
of the nodes are present.

Personal Health Systems (PHS) allow to move the point of care from hospitals to the patient's home. Moreover, a PHS usually handles much more information and provides more appropriate diagnostic and personalized treatments to individuals. In this paper, we present the objectives, structure and expected innovations of the TAMESIS project. TAMESIS aims to contribute in advancing the state of the art of some of the technologies needed for the development of Personal Health Systems. Specifically, we propose techniques for preventing denial of service, sensor node malfunctioning and traffic injection. In addition, we explore a protocol that makes use of mobile agents for the exchange of medical records between networked databases. As a novel aspect, the protocol will not only support bilateral agreements, already existing in the literature, but multilateral agreements. In reference to clinical data, is critical to preserve the privacy and intimacy of patients. Thus, the data, at the time of being collected as for when it is exchanged, should be processed so as to avoid leakage of information that is not strictly necessary for the parties to fulfill their task correctly. A privacy metric suitable for PHS, and the incorporation of mechanisms needed for privacy and intimacy are also key objectives of this project. Finally, usability aspects of all the system interfaces will be considered.

Nowadays, video on demand is one of the services more highly appreciated and demanded by customers. As the number of users increases, the capacity of the system that provides these services must also be increased to guarantee the required quality of service. An approach to that end is to have available several videoservers at various distribution points in order to satisfy the different incoming demands (videoservercluster). When a movie demand arrives to such a cluster, a load balancing device must assign the request to a specific server according to a procedure that must be fast, easy to implement and scalable. In this article we consider the problem of appropriately splitting this load to improve on the system performance. After an analysis of the video packet generation, we point out the similarity between this problem and that of optimally routing packets in data networks. With this similarity in mind, a new mechanism to select the appropriate videoserver is proposed. The purpose of this mechanism is to minimize the average packet transfer time (waiting time plus transmission time) at the videoservercluster. In this way, we are able to obtain a dynamic load balancing policy that performs satisfactorily and that is very easy to implement in practice. The results of several experiments run with real data are shown and commented to substantiate our claims. A description of a practical implementation of the system is also included.

The number of portable electronic devices capable of maintaining wireless communications increases day by day. Such mobile nodes may easily self-configure to form a Mobile Ad Hoc Network (MANET) without the help of any established infrastructure. As the number of mobile devices grows, the demand of multimedia services such as video-streaming from these networks is foreseen to increase as well. This paper presents a proposal which seeks to improve the experience of the end users in such environment. The proposal is called dCW-MMDSR (dynamic Contention Window-Multipath Multimedia Dynamic Source Routing), a cross-layer multipath routing protocol which includes techniques to achieve a dynamic assignment of the Contention Window of the IEEE 802.11e MAC level.
In addition, it includes multipath routing suitable for layered coded video to improve the performance of the service. The operation is simple and suitable for low capacity wireless devices. Simulations show the benefits under different scenarios.

The number of portable devices capable of maintaining wireless communications has increased considerably in the last decade. Such mobile nodes may form a spontaneous self-configured network connected by wireless links to constitute a Mobile Ad Hoc Network (MANET). As the number of mobile end users grows the demand of multimedia services, such as video-streaming, in such networks is envisioned to increase as well. One of the most appropriate video coding technique for MANETs is layered MPEG-2 VBR, which used with a proper multipath routing scheme improves the distribution of video streams. In this article we introduce a proposal called g-MMDSR (game theoretic-Multipath Multimedia Dynamic Source Routing), a cross-layer multipath routing protocol which includes a game theoretic approach to achieve a dynamic selection of the forwarding paths. The proposal seeks to improve the own benefits of the users whilst using the common scarce resources efficiently. It takes into account the importance of the video frames in the decoding process, which outperforms the quality of the received video. Our scheme has proved to enhance the performance of the framework and the experience of the end users. Simulations have been carried out to show the benefits of our proposal under different situations where high interfering traffic and mobility of the nodes are present.